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A Lesson in Shimano 6 speed indexing, and a WTT

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A Lesson in Shimano 6 speed indexing, and a WTT

Old 03-17-18, 10:03 AM
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A Lesson in Shimano 6 speed indexing, and a WTT

OK, I have a 6s indexed Shimano drivetrain (DA shifty bits/600 freewheel) that had run just fine, but as I reinstalled it I decided I really need bigger cogs (I was also changing the crank from a 110 to a 130 on this build).

So, I just plucked a standard Suntour out of the bin - and, the RD wouldn't pull nearly across the width. OK, time to do some comparison. A 6s Ultra was nearly the same height as my 6s Shimano. So let's look at Sheldon's crib sheet. Interesting - Sheldon has no entry for Shimano's 6s indexed spacing. (I didn't break out the calipers, but maybe it's 5.2mm? It is just slightly wider than the Ultra6 overall)

So I tried a couple Ultra6 freewheels. They would work, sort-of, in the stand. Not a good sign for real use on the road. No matter how I fiddled with it, the chain would always jump around on cog#4. I could get all the other cogs settled, at least in the stand. I even tried a modern/narrower 8s chain, too. Same results, same cog. Suntour's spacing on the Ultra6 is just different enough at the big end from the Shimano that this just won't work.

EDIT: see below in post #15 for my digital caliper findings.

So, the verdict is: if you want to index with 6s Shimano, it's probably best to go with a Shimano freewheel or UG cassette.

And, therefore - my WTT:
I have several Ultra6 combos (it's raining and they're out in my shop) ranging - I think - from 13-24 up to 13-27, a 13-28 Suntour standard spaced, and my 13-22 Shimano 600 freewheel.
ISO: to trade any of those for a Shimano 6s indexing freewheel 13-25 to 13-27.
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Old 03-17-18, 10:21 AM
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Although it is often said that standard 6s spacing is the same between Shimano and Suntour freewheels, I have here a couple of Suntour 6s freewheels that are clearly a bit wider than a Shimano 6s freewheel.

Who knew? It's possible to add shims during a buildup of most Suntour freewheels, but I am pretty sure that these were specified with this spacing at the request of some OEM buyer. Using wider cog spacing can make for more-forgiving shifting action when the ratio spread is wider (as on larger freewheels), since unwanted contact between the chain and next-larger cog than the one you are shifting to is reduced (just as with use of a narrower chain, as 9s chain works so well on larger Ultra-6 freewheels).

There have also been 5s freewheels made with wider-than-standard cog spacing, but from much more recent times, and spec'd exclusively on low-end bikes (ostensibly to improve shifting when lower-quality chain, shifter and derailer parts were used). Threw me for a loop because even modern 7-8s Shimano chain wouldn't work on these without creating huge false-neutral zones within the derailer's travel across the freewheel.

But in most (almost all really) cases, standard 6s spacing IS identical between Suntour and Shimano.

And I am assuming that your rear derailer was Dura-Ace to go with your shifters using both of your freewheels(???).

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Old 03-17-18, 12:27 PM
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Originally Posted by dddd View Post
But in most (almost all really) cases, standard 6s spacing IS identical between Suntour and Shimano.

And I am assuming that your rear derailer was Dura-Ace to go with your shifters using both of your freewheels(???).
I assumed the spacing was the same, too ~ 5.5mm like most old 5/6 speed stuff. They're not. My standard spaced Suntour is the same spacing as my 5 speed freewheels.

And yes, all the shifty bits are DA, and it works just peachy with the index-spaced Shimano 600 freewheel (MF-6208) I just wanted a bigger cog, and neither Suntour freewheel I tried would work with either chain. The spacing on those last few cogs is different. I can hold the Suntour freewheels next to the Shimano and see a difference. It surprised me, too. I thought this would be a no-brainer. And my

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Old 03-17-18, 12:56 PM
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Pardon my ignorance but wouldn't a Shimano MF-TZ20 work?
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Old 03-17-18, 01:14 PM
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I think I have a couple of Shimano 6-speed freewheels on hand, but how would I know if they're index compatible? Any particular model #s or just twist-tooth design?
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Old 03-17-18, 04:44 PM
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Maybe I'm way wrong, but I sort of assumed the only Shimano indexing 6-speed was DA until the new 600 SIS came out, and that the DA's freewheel was uniquely DA, but I see he ran the 600 freewheel and it was fine. This after putting 6sp DA indexed on a Cilo, full DA, and having to have the freewheel rebuilt when my relative wore it out. The shop said "DA only" and rebuilt it for $35.00 (REI).

I also assumed there was no Suntour indexing 6-speed, as the early indexing Suntour was 7speed when "they too little, too late(d)" the indexing arena. I do remember restoring an 86 Centurion with Suntour Sprint, and I can't remember if it was indexed or not.

Then again, I exist in a mental fog.
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Old 03-17-18, 06:06 PM
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Suntour had tons of 6 speed indexing systems.

I'm sure that you'd find all the index compatible standard 6 freewheels are 5.5mm spacing. But a Suntour pre-index freewheel might not be.
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Old 03-17-18, 07:35 PM
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Thanks for bringing me up to (6) speed....
Originally Posted by Kontact View Post
Suntour had tons of 6 speed indexing systems.

I'm sure that you'd find all the index compatible standard 6 freewheels are 5.5mm spacing. But a Suntour pre-index freewheel might not be.
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Old 03-17-18, 08:16 PM
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Robbie, you are correct that Shimano indexing began with DA 7400 and then 6208 in '86. But all Shimano 6 speed freewheels from that era up to now have the same spacing and are all indexing compatible. DA freewheels were unique in that the first cog had a different size threaded hole, but the rest of the cogs and spacers are the same as 600 and MF, or at least the same size.

At least as far as I know, which will be corrected as soon as someone more knowledgeable speaks up here.
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Old 03-18-18, 12:03 AM
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Originally Posted by RobbieTunes View Post

I do remember restoring an 86 Centurion with Suntour Sprint, and I can't remember if it was indexed or not.
Two versions of Sprint- one was not indexed, the other was.

The early Sprint stuff has the super cool, ultra fine ratcheting shifters. The other is 6/7 speed Accushift.

Easy way to tell looking at the derailleurs- the Accushift Sprint has a cable tension barrel.


Friction:




Index:


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Old 03-18-18, 03:50 PM
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To the OP, looks like I have a fairly greasy Shimano MFZ-012, 14-32 six-speed freewheel:



Perhaps that's wider range than you're looking for, but PM me if it'll suit your needs.
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Old 03-18-18, 05:28 PM
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Originally Posted by nlerner View Post
To the OP, looks like I have a fairly greasy Shimano MFZ-012, 14-32 six-speed freewheel:


Perhaps that's wider range than you're looking for, but PM me if it'll suit your needs.
Thanks, but my DA RD won't handle that big cog. Plus it would make me spin too much.
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Old 03-18-18, 05:44 PM
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Originally Posted by nlerner View Post
To the OP, looks like I have a fairly greasy Shimano MFZ-012, 14-32 six-speed freewheel:



Perhaps that's wider range than you're looking for, but PM me if it'll suit your needs.
Neal! What a mess! That baby needs some major league spa time.
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Old 03-18-18, 05:51 PM
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That's pretty much how my freewheels look after two rides.
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Old 03-18-18, 06:01 PM
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Broke out the calipers:
From Sheldon Brown's crib sheet, a standard 6s freewheel total width is 29.5mm. My measurements were consistent with that, just slightly wider on the one [non-installed] 6s standard Suntour freewheel I had. Mine averaged 29.6mm as I went around it. Each cog that I could get the calipers on, though I couldn't get to all, were 1.95mm thick, a little narrower than Sheldon's 2.0. So. if you take overall height, subtract the thickness of one cog, and divide by 5, you get a spacing of ~ 5.5mm. That's what we all assumed.

Next - I disassembled a UG 12-17 corncob cassette, unused, and as a recovering Clydesdale it's staying that way , and also measured my MF-6208 freewheeel as best I could.

The freewheel, averaged across several measurements, was about 29.2mm wide. But the more interesting results were from the UG cassette measurements. The first two (smallest cog) positions have integrated spacers. The cog itself was 2.0mm wide, with a total width including the "spacer" of 5.5mm. The third position cog was 1.95mm, while the 4th, 5th and 6th cog were 1.8mm. The spacers had minor variations, but averaged about 3.62mm. So if I add up the cassette, I get 5.5+5.5+1.95+(3*1.8)+(3*3.62) ~ 29.2mm, confirming my overall on the freewheel.

So my measurements reveal that Shimano used 5.5mm spacing for the first positions, then narrowed the spacing slightly. Guess it worked with the indexed drop parallelogram RD. But why make the cogs thinner rather than the spacers? That's an oddity I would not have guessed.

Why these variations add up to not working on cog 4 vs a narrower Ultra6, yet, seeming to work on the other cogs, shifting in the stand, you got me.
I'm going with a Shimano freewheel. Still open for a swap

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Old 03-18-18, 06:07 PM
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Originally Posted by Ex Pres View Post
Broke out the calipers:
From Sheldon Brown's crib sheet, a standard 6s freewheel total width is 29.5mm. My measurements were consistent with that, just slightly wider on the one [non-installed] 6s standard Suntour freewheel I had. Mine averaged 29.6mm as I went around it. Each cog that I could get the calipers on, though I couldn't get to all, were 1.95mm thick, a little narrower than Sheldon's 2.0. So. if you take overall height, subtract the thickness of one cog, and divide by 5, you get a spacing of ~ 5.5mm. That's what we all assumed.

Next - I disassembled a UG 12-17 corncob cassette, unused, and as a recovering Clydesdale it's staying that way, and also measured my MF-6208 freewheeel as best I could.

The freewheel, averaged across several measurements, was about 29.2mm wide. But the more interesting results were from the UG cassette measurements. The first two (smallest cog) positions have integrated spacers. The cog itself was 2.0mm wide, with a total width including the "spacer" of 5.5mm. The third position cog was 1.9mm, while the 4th, 5th and 6th cog were 1.8mm. The spacers had minor variations, but averaged about 3.62mm. So if I add up the cassette, I get 5.5+5.5+1.95+(3*1.8)+(3*3.62) ~ 29.2mm, confirming my overall on the freewheel.

So my measurements reveal that Shimano used 5.5mm spacing for the first positions, then narrowed the spacing slightly. Guess it worked with the "new" indexed drop parallelogram RD. But what make the cogs thinner rather than the spacers? That's an oddity I would not have guessed.

Why these variations add up to not working on cog 4 vs a narrower Ultra6, yet, seeming to work on the other cogs in the stand, you got me.
I'm going with a Shimano freewheel. Still open for a swap
So your 6 speed index system won't work when you go from a 29.2mm wide freewheel to a 29.6?
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Old 03-18-18, 09:56 PM
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Originally Posted by pastorbobnlnh View Post
Neal! What a mess! That baby needs some major league spa time.
Yup, it is, Bob! Iím likely sending this one your way soon.
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